Alloys



Patented May 29, 1945 UNITED STATE s PATENT OFFICE} ALLOYS No Drawing.Application September 1, 1943, Serial No. 500,842

'7 Claims.

Our invention relates to the preparation of alloys which areparticularly resistant to the action of sulphur-containing gases buthave other utilitie as well, including resistance to scaling at hightemperatures such as up to about 1600 degrees F. l

The alloys to which our invention relates contain from about 3% to about12% aluminum,- from about.45% to about 75% iron, from a fraction of 1%,for example, 0.15%, up to about 10% of chromium, balance substantiallyall manganese, the manganese constituting at least 20% of the alloy. Apreferred embodiment of our invention encompasses alloys containing fromabout 5% to about aluminum, from about 2% to about 10% chromium, fromabout 20% to about 50% manganese, balance substantially all iron. Wehave found that when these alloys are made from manganese of highpurity, particularly electrolytic manganese, preferably at least 99.0%

pure and especially at least 99.9% pure, and commercially pure forms ofaluminum, chromium and iron, their ductility tends to be enhanced andmany of them, particularly those in which the chromium content does notsubstantially exceed about 2%, may be rolled and drawn into wire. Withincreasing percentages of chromium the ductility of the alloys isprogressively lessened.

The following examples are illustrative of the preparation of alloyspursuant to our present invention. It will be understood that thesealloys and their mode of preparation are merely illustrative of thepreparation of alloys in accordance with the present invention and arenot to be construed as in any manner liinitative of the full scope ofourinvention, the latter being set out in the claims.

Example I Percent Iron 72 Manganese 20 Aluminum 6 Chromium 2 In thepreparation of this alloy, a low carbon ingot iron is first melted withthe required amount of metallic manganese. A we have pointed out above,we prefer particularly to use electrolytic manganese having a purity ofthe order of at least 99.0%, but other manganese of high purity may beused. We then add the aluminum and finally the chromium. The chromium ispreferably added in the form of a low carbon ferro-chro- Example IIIPercent Manganese -25 Aluminum .5 Chromium l 1 Iron 69 Example IV Percent Manganese 22 Aluminum 8 Chromium 2 Iron Example-V Per centManganese 30 Aluminum 6 Chromium", 3

cold rolled or otherwise worked. When heated to temperatures of theorder of 1400 degrees F. to 1600 degrees F., it forms a thin surfacecoating but does not scale even after long hours of heat- Example IIPercent Iron 64 Manganese 20 Chromium 10 Aluminum 6 This alloy may bemade in the manner de scribed in Example I. It is advantageous, however,from the standpoint of cost, and also from the standpoint of producingbetter ductility in the resulting alloy, to utilize an alumino-thermicreduction procedure. This is accomplished by mixing iron oxide of highpurity, such as mill scale, with manganese, dioxide of high purity,together with chromite concentrates of high purity. This mixture,properly proportioned. based on it analysis, is mixed with an amount ofpowdered aluminum so calculated that the correct amount of residualaluminum will be present in the final alloy. The mixture is then ignitedand the resulting molten alloy cast into the desired shape. Since theamount of aluminum which remains in the alloy is somewhat determined bythe specific conditions under which the reduction reaction takes place,preliminary tests or experimentsshould be carried out in connection withany given reduction procedure utilized in thepreparation of the alloy.The reduction of residual aluminum increases the ductility of this alloywith only slight loss of scale-resistant properties if the aluminum isnot reduced below 3%.

Examples of other alloys which may be made in accordance with ourinvention are as follows.

Iron 61 I: trolyte.

acids better than stainless steel.

7 As we have pointed out in the Example I, the

carbon content of the alloys should be kept at a minimum and in no caseshould exceed 0.15%.j

The alloys may contain up to about 2% of silicon in the form of theelement or, in other words, 'el'e-i mentary silicon, as distinguishedfrom silicon oxides.' It is important, if the ductility and othercharacteristics of our alloys are not to be im paired, that oxides ofsilicon, which are frequent-I ,filed October 20, 1941, now Patent 5.

part of our prior application, SerialjNo. 415,769,

issued September 14,1943. 7 V r 7 'What we claim as new anddesire'to'protect by Letters Patent of the United States is:

'from 45% to 75% iron, balance substantially all 1y present insilicon-reducedjmanganese and .chrornium,.,, and aluminum-reducedmanganese:

and chromium, benot present in our alloys or, if present, the amountsthereof should be exceeda ingly' small,not over approximately 0.2% andpreferably less or totally absent.

'The alloys of our present invention have, in}

T general, low linear coefficients of expansion whichf renderthem usefulin connection with production of bi-m'etal strips or other expansionelements or units; The electrical resistance of the alloys of ourpresent invention is, in "general, quite high and said'alloys are,therefore, of utility for the; manufacture of heating elements operatingat moderately'high temperatures.

Weihave also found that the alloys of our present invention may beanodized to provide them with acoating of a continuous film of alu-fl 7'minum oxide. This film .or coating may be placed manganese, themanganese constituting at least 20% of the alloy. 7

2. Alloys containing from 5 to 10% .alu-

minum, from 0.15% to about 10% chromium,

from 20% to mangan'ese;'balance SllbStfiIl.

tially all iron, the alloy being made with aluminum, manganese, and ironof high purity.

3. Alloys containing. from 5% to 10% ;alu-

minum, from 0.15% toabout 10% chromium,

from 20% to 50% electrolytic manganese'having a purityof at least 99.0%,balance substantially all iron, the iron constituting from 45% to of thealloy.- 7

4. Alloys containing minum, from 0.15% to about 2% of chromium, from 45%to 75% iron, balance substantially all 'manganesqthe manganese.constituting at least 20% of the alloy.

upon the alloys by the w'ell-known'so-called 'ano dizing process,that'is, by making the alloy the anode of an electrical :circuitin asuitable elec- Such anodized alloys, in certain in-'' stances, appear towithstand the action of dilute 5. An alloy' containing about 72% iron,about 20% manganese, about 6% aluminum, and about 2% chromium.

s 6. An alloy containing 3% to 12%aluminum," I 2% to l0%wchromium,45% to75% iron, balance 7 substantially all manganesathe manganeseconstitutingat least 20% of the alloy. 7 r ,7 7. An alloy containing about 64% iron,about 20% manganese, about 10% chromium, and about 6% aluminum.

REGINALD S.DEAN.- V CLARENCE T. ANDERSON.

Our present application is-a continuation-in No. 2,329,186, r

1. Alloys containing from 3% to 12%aluminum', from 0.15% to about 10%chromium,

from 3% to 12% alu-

